Detalle de la pared esporal de “M” panniformis, escala = 500 nm E Corte longitudinal

The developed inventory system has been tested in the forest of Thessaloniki, Greece to assess the non-timber functions protection against erosion and water percolation. The evaluation of the external factors of the functions resulted in a division of the forest area into possible homogeneous zones for which management prescriptions have been drawn. This prescriptions have been further completed with specific silvicultural treatments for each forest stand, on the basis of the evaluation results of the internal factors.

To make this information available to the praxis, it should be incorporated in the forest management plans. The measures derived from the evaluation of the external factors are not directly related to the forest stands themselves, but they are rather forest policy measures (e.g. land use changes, intensity of recreation, density of road network) aiming at the regulation of human intervention in the forest in way to reduce negative impacts on water percolation and erosion. These measures can be presented in detail in a chapter of the forest management plan, together with the explanation of the reasons for which they should be forced.

On the other hand, the measures derived for from the evaluation of the internal factors are prescribing interventions in the forest stands. As already mentioned in chapter 2.3.2, forest management plans in Greece end up with a Stand Description Sheet for each forest stand∗ in which all recorded information together with evaluation results and the proposed silvicultural measures for the stand handling appears. The evaluation results of the non- timber functions should therefore be integrated in the stand description sheets.

Geographic information systems are a valuable tool that facilitates the integration task, since the entire information is spatially referenced. The zones resulted from the clustering of the land units of the internal factors are spatially explicit and consequently the derived silvicultural treatments and other measures can be spatially allocated and illustrated on a map.

A separate map for each function can easily be constructed, but it is more practical and convenient for the praxis to have only one map, where all appropriate measures appear. Therefore, the proposed silvicultural and other measures for all functions (the timber function included) should be assembled and compiled separately for each stand. This procedure would also lead to identification of contradictory measures for the same stand, which should be resolved.

∗ _{It is reminded here that stand in the Stand Description Sheets is mind as an administrative subdivision} (compartment) of maximum 50 ha size, permanently marked in the forest and not to the stand in silvicultural sense. For each compartment in figures 35 & 36 is a separate stand description sheet to be constructed.

In the following figures 35 and 36, respective maps of the two functions and for the first three compartments of the forest of Thessaloniki are presented. Separate maps for each function have been here constructed to demonstrate the integration for more than one functions and discuss problems that may arise.

1

2

3

N

250 0 250 Meters

Loosen canopy closure and improve stand structure in the direction of heterogeneous multi-storey stand. Stands with low canopy closure. Favor natural regeneration or apply planting.

Well structured closed stands. Maintain existing structure. Compartment boundaries

L E G E N D

Figure 35: Stands of three compartments of the forest where similar measures regarding the water percolation function should be applied.

1

2

3

N

250 0 250 Meters

Loosen canopy closure and improve stand structure in the direction of heterogeneous multi-storey stand. Stands with low canopy closure. Favor natural regeneration or apply planting.

Well structured closed stands. Maintain existing structure.

Compartment boundaries L E G E N D

Figure 36: Stands of three compartments of the forest where similar measures regarding erosion protection should be applied.

It should be noted here, that the maps have been produced from the inventory data of a systematic plot sampling with plots located at the middle of each grid-square and it is

assumed that plot conditions represent the conditions of the entire area within a grid- square. How far from the plot the conditions change is not known. Nevertheless, grid cells provide a picture of the variability in the stands and particularly the allocation in space of the various situations.

A visual comparison of the two maps shows great agreement in the west and north part of compartment 1 and in the entire compartment 3. Contradictory measures are proposed for overall eight cells, marked with a circle in both maps. For three cells in compartment 1 measures should be taken to loosen canopy closure for the water percolation, while for prevention of erosion danger the conditions are optimum and stand structure should remain as is. Similar is the situation in another cell in compartment 2. For the remaining four cells the situation is more opposing. While for one function measures should loosen canopy, for the other function canopy closure should be increased.

Since the two functions considered, water percolation and erosion, are complementary and measures taken to improve the conditions for one contribute also positive to the other, the contradiction arisen for these eight cells should be attributed to weakness of the evaluation methodology and considered as a failing of the evaluation procedure.

To resolve this problem, the members of the inventory crew, as well as foresters of the forest service of Thessaloniki have been consulted. Both have confirmed that the conditions in the eight cells are better depicted by the evaluation of the water percolation function. They have also confirmed that the pattern of stand conditions pictured in the map corresponds generally with the actual conditions encountered in the forest.

Consequently, a map as the one in figure 35 for each forest compartment can be constructed at desired scale and attached to each stand description sheet to help the forester responsible for the implementation of the proposed measures to localize them within the stands.

The measures proposed here in favor of the water percolation and erosion function may of course affect the respective measures taken for the timber production function. But this case has not been examined. Generally, the problem of contradictory measures with respect to different functions would be much more difficult to resolve, when more than two and particularly non complementary functions would be considered. A solution to the problem could be the quantification of the relative importance of the various functions (resulting from the forestry policy applied) and its use as a measure to regulate the intensity of the measures taken for each function. Methods to resolve such problems can be found among others in ZANGEMEISTER (1976) and SAATY (1980). GATZOJANNIS (1984) has applied such methods in a case study in Greece.